Not me, I’m running all that expensive oem/ZF trans service, diff, and trans case fluid. Saving containers and using FCPEuro’s warranty program makes the cost closer to $335 instead of $600. I just need to preload the next service and keep items on hand and ready to return the service items. All legit, and confirmed multiple times by reps in different venues.

Purchase initial kit and fluids -$600
Perform service and drive x miles
Purchase another identical set - $600
Perform service and return all used parts and fluids -$75
-$1275
Receive credit back to card for $600
-$675 for two full service kits (obviously trans miles vs what’s needed for diff and trans case is different)
-$335 cost per kit if you are willing to do that legwork.

I wonder if some of the transfer case issues stem from the fact that (at least on the E60 and F10 chassis) you need to lower/move the exhaust to even access the transfer case, and there's no drain so you have to pull it out, invert, refill, and re-install. Then put the exhaust back. Oh, and then have the dealer tell the car's ECU about the replaced fluid. So maybe lots of owners just blow this maintenance off until the thing fails.

FWIW, a (well-respected, well-known, not on tdiclub) BMW guru recommends 50k fluid changes. I am guilty of holding off with a fluid change on my wife's car (currently at just shy of 90k) but will have to bite the bullet at some point. Cheaper to do the maintenance.